KR20080000668A - Sub-pixel mapping - Google Patents

Abstract

A method of mapping a four primary input signal (IS) to sets (Pij) of four sub-pixels (RPij, GPij, BPij, WPij) of a display device (DD). The four primary input signal (IS) comprises a sequence of input samples (Sij) each comprising a value for a first input signal (Rlij), a value for a second input signal (Glij), a value for a third input signal (Blij), and a value for a fourth input signal (Wlij). The sets (Pij) of the four sub-pixels comprise a first sub-pixel (RPij) to supply light having a first primary color (R), a second sub-pixel (GPij) to supply light having a second primary color (G), a third sub-pixel (BPij) to supply light having a third primary color, and a fourth sub-pixel (WPij) to supply fourth light having a fourth color (W), the first, second, third and fourth color all being different, and the fourth color being within the color gamut of the first, second, and third color. The method comprises sub-sampling (MAP) the input samples (Sij) of the four primary input signal (IS) by assigning the first input signal (RI11), the second input signal (GI11), and the third input signal (BI11) of a particular input sample (Sl 1) to the first (RP11), second (GP11) and third sub-pixel (BPl1) of a particular set (P11) of four adjacent sub-pixels, respectively, and by assigning the fourth input signal (WI12) of a further input sample (S12) to the fourth sub-pixel (WP11) of said particular set (S11) of the four adjacent sub-pixels, wherein the particular input sample (S11) and the further input sample (S12) are associated with adjacent positions on the display device (DD).

Description

Sub-pixel mapping {SUB-PIXEL MAPPING}

The present invention relates to a method for mapping a four primary color input signal to four sub-pixels of a display device, a computer program product, a system for mapping a four primary color input signal to four sub-pixels of a display device. And a circuit for driving the display device and including the system, a display apparatus including the circuit, a portable device including the circuit, a broadcast system, and a broadcast method.

Current displays generally have three different color sub-pixels with three primary colors, R (red), G (green), and B (blue). These displays are driven by three input color signals, where the RGB signals are preferred for displays with RGB sub-pixels. The input signals may be any other related three signals, such as for example YUV signals. However, these YUV signals must be processed to obtain RGB drive signals for RGB sub-pixels. Typically, these displays with three different color sub-pixels have a relatively small color gamut.

If the fourth sub-pixel produces a color outside the color range defined by the colors of the other three sub-pixels, the displays with four sub-pixels with different colors provide a wider color range. Alternatively, the fourth sub-pixel may generate a color within the color range of the other three sub-pixels. The fourth sub-pixel may generate white light. Displays with four sub-pixels are also called four primary colors displays. Displays with sub-pixels that emit R (red), G (green), B (blue), and W (white) light are commonly referred to as RGBW displays.

In general, displays having four or more different color sub-pixels are also called multi-primary displays. N drive signals for the N primary colors of the sub-pixels are calculated from the three input color signals by solving a series of equations defining the relationship between the N drive signals and the three input signals. Since N unknown drive signals have to be determined, only three equations are applicable, so many solutions are usually possible. Multi-primary conversion algorithms convert three input color signals into N drive signals by selecting one of many possible solutions.

However, mapping a three-primary input signal into four primary color sub-pixels presents a great challenge. If all sub-pixels in one pixel receive the driving value from the same input pixel, the addition of the fourth sub-pixel reduces the resolution of the display. To restore the resolution, the conversion of the three-primary input signal into four drive signals is achieved by sub-sampling operation (factor 2) by mapping two or more input samples to one group of four sub-pixels. ). The input signal typically contains RGB components and assumes a uniform rectangular grid of display pixels. However, a uniform rectangular grid of these display pixels is lost by sub-sampling and mapping. Sub-sampling results in color artifacts depending on the values of the three components of the three-primary input signal.

 It is an object of the present invention to reduce the loss of resolution and to provide a method of mapping a four primary color input signal to four sets of sub-pixels of a display.

A first aspect of the invention provides a method of mapping a four primary color input signal to sets of four sub-pixels as described in claim 1. A second aspect of the invention provides a computer program product as described in claim 8. A third aspect of the invention provides a system for mapping a four primary color input signal to sets of four sub-pixels of a display device as described in claim 10. A fourth aspect of the invention provides a circuit for driving a display device as described in claim 11. A fifth aspect provides a display device as described in claim 12. A sixth aspect provides a portable device as described in claim 13. A seventh aspect provides a broadcast system as described in claim 14. An eighth aspect provides a broadcast method as described in claim 15. Advantageous embodiments are defined in the dependent claims.

The present invention relates to mapping samples of a four-primary input signal to sets of four sub-pixels of a display device. It is assumed that the conversion from the three input color signals to the four primary color input signals has already been performed. Alternatively, the four-primary input signal may be generated by a secondary device such as a camera, server, or video processing device. The 4-primary input signal comprises a sequence of input samples, each input sample comprising a value for a first component, a value for a second component, a value for a third component, and a value for a fourth component It contains four sub-samples. These values of the sub-samples are referred to as components of the samples or simply components.

The sets of four sub-pixels comprise a first sub-pixel for providing light with a first color, a second sub-pixel for providing light with a second color, and providing light with a third color. A fourth sub-pixel for providing light having a third sub-pixel, and a fourth color). The first, second, third, and fourth colors are all different, and the fourth color is within the color range of the first, second, and third colors.

The method includes a sub-sampling procedure of sub-sampling samples of the four primary color input signal. The first component, the second component, and the third component of the first input sample are assigned to the first, second, and third sub-pixels of a particular group of adjacent sub-pixels. The fourth component of the second input sample is assigned to the fourth sub-pixel of this same particular group of adjacent sub-pixels. A first input sample and a second input sample are associated with adjacent locations on the display device. Thus, the fourth component of the first input sample, and the first, second, third components of the second input sample are not assigned to the sub-pixels of the particular group of adjacent sub-pixels. Preferably, these components of the first and second input samples are not produced or transmitted, which provides more effective multicolor conversion. This also has the advantage that no filtering is required before mapping. In fact, the mapping / sub-sampling is very simple, so it can be part of a multi-primary conversion (ie, the multi-primary conversion outputs the same sub-pixel values as needed on the display).

This sub-sampling process defines the luminance component for the fourth color because both the group of first, second, and third input components of the first input sample and the fourth input component of the second sample define a luminance component for the fourth color. This is done in such a way that little loss can be noticed. In addition, transformations and mappings present significant color defects in that the colorless (grayscale) image remains colorless.

Thus, this special mapping algorithm has the main advantage that both the group of first, second and third sub-pixels on one side and the fourth sub-pixel on the other side reproduce luminance information for the color of the fourth sub-pixel. Has

Also, color errors will not occur in the color associated with the fourth color component. For example, a first sub-pixel displaying black and white information and providing red light, a second sub-pixel providing green light, a third sub-pixel providing blue light, and providing white light When using the fourth sub-pixel, the color errors do not occur because the group of first, second, third sub-pixels can provide white light. If the fourth sub-pixel has another color, the first, second, and second colors are within the range of colors that can be generated by the first, second and third sub-pixels. It is possible to produce the same color with, and third sub-pixels.

On the other hand, if the mapping does not include assignment of components of the same input sample to the first, second, and third sub-pixels, then if the fourth sub-pixel provides white light, then the black and colorimetric information is obtained. Color errors occur when displaying.

In the embodiment claimed in claim 3, the display device is illuminated by a backlight unit. Thus, the light provided by the sub-pixels is obtained by adjusting the generated light generated from the backlight unit. To obtain red, green and blue light, the red, green and blue filters are associated with the first, second and third sub-pixels respectively. Light provided by the backlight unit passes through the unfiltered fourth sub-pixel. Of course, all the sub-pixels, and thus the fourth sub-pixel, can also adjust the intensity of the generated light in response to the driving voltage determined by the associated component. Preferably, the light provided by the backlight unit is white. Alternatively, however, the light of the backlight unit may have a different color, and the colors of the first to third sub-pixels may be different from red, green, and blue. This is particularly interesting for displays that apply different (more blue) white-dots (which are still referred to as "white"). Also of interest for color continuous displays, where the backlight is white on average except red / green / blue in alternating frames, but the sub-pixels on the display are still RGBW.

In the embodiment as claimed in claim 5, in the four-primary input signal, to correspond to the position of the fourth sub-pixel with respect to the sub-group of the first, second and third sub-pixels in the set of sub-pixels. , Other input samples are located relative to a particular input sample. This provides the optimum timing of the input samples for the sub-pixel arrangement. The fourth sub-pixel may be in the same horizontal line (row) or vertical line (column) on the display screen. However, other geometric arrangements are possible, for example, the fourth sub-pixel can be in adjacent lines at the center positions of the first, second, and fourth sub-pixels.

In an embodiment as claimed in claim 6, the second input sample immediately precedes or follows the first input sample in the first line of the video input image. The first, second, third components of the first input sample are used to drive the first, second, and third sub-pixels of the first set of sub-pixels. The fourth component of the second input sample is used to drive the fourth sub-pixel of the first set of sub-pixels.

In addition, the third and fourth input samples are sub-sampled into a second set of sub-pixels. A second set includes a fifth sub-pixel for providing light with the first color, a sixth sub-pixel for providing light with the second color, and a second sub-pixel for providing light with the third color. Seven sub-pixels, and an eighth sub-pixel for providing light having the fourth color. The sub-sampling assigns a first component, a second component, and a third component of the fourth input sample to each of the fifth, sixth, and seventh sub-pixels, and the fourth component of the third input sample. Is assigned to the eighth sub-pixel. The fourth input sample immediately precedes or follows the third input sample in the second line of the video input image. The second line immediately precedes or follows the first line. Note that the lines of the video input image may extend in the horizontal or vertical direction. In the horizontal direction, the input samples directly follow each other in time. In the vertical direction, the input samples are delayed one line time with respect to each other.

In the embodiment described in claim 7, the mapping according to the present invention proceeds by converting a three primary color input signal into a four primary color input signal. This conversion is made under the same brightness constraint on the brightness of the combination of the first sub-pixel, the second sub-pixel, and the fourth sub-pixel on the other hand. This has the advantage that the luminance difference between the fourth sub-pixel and the group of first, second and third sub pixels is minimal.

These and other aspects of the invention will be apparently understood with reference to the embodiments described below.

1 shows a prior art mapping a three primary color input signal to a display with three primary color sub-pixels.

2 is a schematic diagram of a portion of an LCD display having four sets of sub-pixels and illuminated by a backlight unit.

3 is a block diagram of a display device including a system for mapping a four-primary input signal to sets of four sub-pixels.

4 illustrates mapping a four-primary input signal to a display with sets of four primary color sub-pixels in accordance with the present invention.

FIG. 5 illustrates a broadcast system providing information including signals for driving four primary color sub-pixels. FIG.

6 is a schematic diagram of a display device including a system for converting a three-primary input color signal into an N-primary drive signal.

7 shows a graph for explaining an implementation example of an additional equation.

8 shows a graph for explaining another embodiment of the additional equation,

9 is a block diagram of an example of an implementation of the conversion according to the present invention.

Note that items having the same reference numerals in different drawings have the same structural features and the same functions or the same signals. The function and / or configuration of these items is described with respect to particular drawings, and the repeated description thereof is not necessary in the detailed description of another drawing.

In references beginning with a constant number of uppercase letters followed by i and / or j characters, i and j are indexes. These indices i and j generally indicate an item indicated by an uppercase letter (s) or may indicate any one of the items indicated by a reference. If a particular one of the items is specified, the indices are replaced by numbers. For example, if an uppercase letter P is used to indicate pixels of a matrix display, Pij represents all of the pixels of the matrix display or one of these pixels. Pmn, on the other hand, represents pixels in the mth row and nth column. The indices used in the claims are only those shown in the figures and should not be construed as limiting the scope of the claims.

Figure 1 shows the prior art of mapping a three primary color input signal to a display with sets of three primary color sub-pixels.

The display device DD is shown on the right side as a matrix display in which pixels Pij are arranged in m rows and n columns. The first row includes pixels P11, P12, ..., P1n, the second row contains pixels P21, P22, ..., P2n, and the last row contains pixels Pm1-. Pmn). Each of the pixels Pij includes three sub-pixels RPij, GPij, and BPij. In Fig. 1, only the sub-pixels Rpl1, GPl1, BPl1 are indicated by reference.

The three primary color input signal TIS is shown on the left. The three primary color input signal TIS is also called an input signal and includes a sequence of input samples Iij. Each of the input samples contains three values. This is a first value defining the red component Rij, a second value defining the green component Gij, and a third value defining the blue component Bij. In Fig. 1, for one frame of the input image, only the samples Il 1, I12 and I1n of the first line of the input image, the samples I21 and I22 of the second line of the input image, and the input image Only samples Sm1 and Smn of the last line of are shown. In the first line, only the components R1, G1, B1, and R1, G1, B12 are indicated. Although the samples Iij of the three-primary driving signal are normally supplied continuously in time, the writing of the samples Iij by synchronizing the writing of the samples Iij to the pixels Pij with the generation of the samples Iij. Although the mapping of the display to the correct pixels Pij is made, in the left metric of FIG. 1, the samples are considered to be organized to already have an exact association with the position on the display device DD.

The conventional mapping technique is very simple, the input sample Iij is intended to be displayed on the corresponding pixel Pij, the first component Rij is used to drive the first sub-pixel RPij, and the second component ( Gij drives the second sub-pixel GPij, and the third component Bij drives the third sub-pixel BPij. Of course, the color association between the components and the sub-pixels must match. Typically, the first value Rij is the red component of the input sample Iij, the first sub-pixel RPij provides the red light, the second value Gij is the green component of the input sample Iij, The second sub-pixel GPij provides green light, the third value Bij is a blue component of the input sample Iij, and the third sub-pixel GPij provides blue light. Of course, the order of the sub-pixels GPij may be different.

Thus, the mapping in the conventional system was a simple one-to-one mapping. However, this mapping is further complicated if the original three-primary input signal (TIS) is to be displayed on a display with four sets of sub-pixels. The original three-primary input signal TIS must first be converted to a four-primary input signal IS whose four components match the four colors of the four sub-pixels. If each one of the four components of the input samples Sij of the four primary color input signal IS has a one-to-one mapping with four sub-pixels, the resolution of the display is reduced (if four and three). If the dimensions of the sub-pixels of the two sub-pixel displays are the same) or the light output per sub-pixel is reduced (if the resolution remains constant). These problems can be solved by sub-sampling the four primary drive signals by a factor of two. This means that two input samples are mapped to the same set of four sub-pixels.

The present invention focuses on the specific mapping of input samples to four sub-pixels. Specific mapping will be described with reference to FIGS. 3 and 4. First, in FIG. 2, a specific implementation of the display device DD is described.

Figure 2 schematically shows a part of an LCD display which has four sets of sub-pixels and is illuminated by a backlight unit. The LCD display has sets of four sub-pixels (RPij, GPij, BPij, WPij) of LCD material, the conversion of which can be controlled in a known manner by applying a drive voltage to the LCD material. Polarizers and support substrates of the LCD display are not shown. Four sub-pixels RPij, GPij, BPij, WPij are illuminated by light BLL generated by backlight unit BL. Only two sets Pij of four adjacent sub-pixels RPij, GPij, BPij, WPij are shown. The first color filter RF is associated with the sub-pixels RPij, the second color filter GF is associated with the sub-pixels GPij, and the third color filter BF is the sub-pixels. Associated with (BPij). Color filters RF, GF, BF filter different colors, such that the associated LCD sub-pixels provide different spectral portions of light BLL. These different spectral parts may partially overlap. There is no color filter associated with the sub-pixel WPij, so the color of the light by the sub-pixel WPij is the same as the color of the light BLL. The color filters RF, GF, and BF are selected such that the mixed light of the sub-pixels RPij, GPij, and BPij can have the same color as the light BLL.

Preferably, the color filters RF, GF, BF are red, green, and blue filters, respectively, and the light BLL is white light.

3 shows a block diagram of a display device including a system for mapping a four-primary drive signal to sets of four sub-pixels. The system starts with a three-primary input signal TIS having samples Iij each comprising a Rij (normal, red) component, a Gij (normal, green) component, and a Bij (normal, blue) component. A multi-primary converter MPC converts the three-primary input signal TIS into samples Sij of the four-primary input signal IS. Samples Sij of the four-primary input signal IS include RIij, GIij, BIij, WIij, components. Such multicolor converters are well known.

The sub-sampler or mapper MAP according to the invention maps the samples RIij, GIij, BIij, WIij to a four-primary output signal OS, which is the sub-samples RPij for each sample Dij, respectively. , Four components (RDij, GDij, BDij, and WDij) for driving GPij, BPij, and WPij. The backlight unit BL emitting the display DD and backlight BLL is only schematically shown. Preferably, the display DD is a matrix display. The display DD may be the LCD shown in FIG. 2, or may be another display capable of adjusting the light BLL from the backlight unit BL. Adjustment of light can be obtained by varying the reflectance or transmission of the sub-pixels RPij, GPij, BPij, and WPij. The backlight unit BL may adjust the intensity and color of the light BLL. In displays in which sub-pixels emit light, such as LED displays, the backlight unit BL can be omitted.

The display device may be any other device having a display such as a television, a computer monitor, or a portable device, for example, for mobile communication or personal use (eg, a personal digital assistant (PDA), or an electronic book).

4 illustrates mapping a four primary color input signal to a display having sets of four primary color sub-pixels in accordance with an embodiment of the invention. Figure 4 shows two contiguous blocks of four contiguous sub-pixels in a particular block of four contiguous input samples 111, 112, 121, 122 of a multi-primary color conversion (MPC) and three primary color input signal (TIS). 4 shows the processes of mapping (MAP) to sets (shown on the right side of FIG. 4 and showing only two sets of four sub-pixels of display DD for clarity). The first contiguous set P11 of four contiguous sub-pixels comprises sub-pixels indicated by RP1, GP1l, BP1l, and WP11, which in this example is of the pixels of the display screen of the display device DD. Represent the first four sub-pixels on the first row. The second adjacent set of four adjacent sub-pixels P21 includes the sub-pixels indicated by RP21, GP21, BP21, and WP21. The same processes apply to the remaining sets of four adjacent sub-pixels Pij in the remaining blocks of four adjacent samples of the three primary color input signal TIS. The mapping according to the invention can be used advantageously for other geometric distributions of sets of sub-pixels. Before describing the multi-primary color conversion (MPC) and mapping processes (MAP), various signals of FIG. 4 are first described.

Sample I11 comprises components R11, G11, B11, sample I12 comprises components R12, G12, B12, and sample I21 comprises components R21, G21, B21. And sample I22 comprises components R22, G22, B22. In fact, the three-primary input signal (TIS) is a sequence of samples each comprising three components. The components Rij, Gij, Bij of each sample Iij define the contribution to the color of the sample Iij of the three primary colors associated with the three components Rij, Gij, Bij. The sample Iij drives a first sub-pixel in which the first component Rij emits light having a color that matches the primary color associated with the first component, and the primary component Gij is associated with the second component. Driving second sub-pixels that emit light with a color that matches with the third component Bij driving third sub-pixels that emit light with a color that matches the primary color associated with the third component Is considered to be displayed on the display. Thus, a group of three sub-pixels may display a color range defined by three different primary colors of the three sub-pixels. Preferably this color range best matches the color range defined by the three primary colors of the samples Iij. Typically, the three primary colors of the components Rij, Gij, Bij of the samples Iij and the three primary colors of the sub-pixels are RGB (red, green, and blue).

The multi-primary conversion MPC converts the input samples I11, I12, I21, I22 into additional samples S11, S12, S21, S22 of the four-primary input signal IS. Sample S11 comprises components RIl1, GIl1, BIl1, WIl1, and sample S12 comprises components RI12, GI12, BI12, WI12, and sample S21 comprises components RI21, GI21, BI21, WI2, and sample S22 includes components RI22, GI22, BI22, WI22. Components RIij are considered to be displayed on sub-pixels with a first color, components GIij are considered to be displayed on sub-pixels with a second color, and components BIij ) Is considered to be displayed on the sub-pixels with the third color, and the components (WIij) DMS are considered to be displayed on the sub-pixels with the fourth color. Thus, the original three primary color input signal TIS must be displayed on sets Pij of four sub-pixels RPij, GPij, BPij, WPij. The multi-primary color conversion (MPC) takes into account primary colors of three components and four sub-pixels (RPij, GPij, BPij, WPij) colors, and calculates values of three components per sample (Iij) per sample (Sij). It must be converted into values of four components.

Such multicolor conversion (MPC) is well known. The invention points to a special case mapping algorithm MAP in which the fourth color WPij of the sub-pixels is within the color range defined by the first, second and third colors. The mapper MAP has many possibilities for mapping the four primary color input signal IS to the four primary color output signal OS. The four-primary output signal OS includes samples including components RDij, GDij, BDij, WDij, which respectively drive four adjacent pixels RPij, GPij, BPij, WPij of the same set Pij. (Dij) is included.

It is possible to map the components RIij, GIij, BIij, WIij of the 4-primary color input signal IS to the components RDij, GDij, BDij, WDij of the 4-primary color output signal OS. Thus, all four-primary input signals Sij are displayed in a set of four sub-pixels Pij. However, if the luminance should not be sacrificed, the addition of the fourth sub-pixel results in a decrease in the resolution of the display DD. Or if the resolution is maintained, the brightness per sub-pixel is reduced.

In order to restore the resolution, the mapping of the 4-primary input signal IS to the 4-primary output signal OS maps two input samples Sij to four adjacent sub-pixels RPij, GPij. Sub-sampling operation by factor 2 by mapping onto one set Pij of BPij, WPij). The original three-primary input signal TIS assumes a uniform rectangular grid of display pixels and their sub-pixels. The mapping MAP further reduces color defects in the color of the fourth sub-pixel WPij.

Special mapping (MAP) according to the invention alleviates color defects. The basic concept is that two samples S1l and Sl2 (or S21 and S22) are mapped to one set Pl1 (or P21) of four sub-pixels RPij, GPij, BPij, WPij in the following way: Will be. The specific sample Dij of the 4-primary color output signal OS is the first component RDij which is the first component RIij of the first sample S11 and the second component GIij of the first sample S11. The second component GDij, the third component BDij which is the third component BIij of the first sample S11, and the fourth component WDij which is the fourth component Wiij of the second sample S12 Have Thus, two consecutive samples Sij of the four primary color input signal IS are converted into one sample Dij of the four primary color output signal OS. Three primary colors that can together provide the same luminance as the four primary colors come from one of two adjacent samples Sij, and the fourth primary color comes from the other one of the two samples Sij. The same lasts for all other two adjacent samples Sij. This has the advantage that no luminance errors occur because the other three sub-pixels RPij, GPij, BPij of the same set Pij can provide the same luminance. This approach also allows the luminance to be divided into a set of fourth sub-pixel WPij on the one hand and first, second and third sub-pixels RPij, GPij, BPij on the other hand without causing color errors. Has the advantage that it can.

In a preferred embodiment, the mapping (MAP) according to the invention comprises a multi-primary conversion (MPC) which converts a 3-primary input signal (TIS) into a 4-primary input signal (IS) under the same luminance constraints per sample. The luminance of the three components RIij, GIij, BIij is equal to the luminance of the fourth component WIij, which is combined and possibly produces the same color as the fourth component WIij, depending on the input color. . Such multi-primary conversion under the same luminance constraints is described in the patent application of application number PH000227EP1 filed on the same date as the present patent application and described with reference to Figs.

The mapping shown in FIG. 4 is a special example showing an advantageous mapping of adjacent rows of sub-pixels RPij, GPij, BPij, WPij to adjacent sets Sij, where sub-providing a fourth light is provided. The pixels WPij are actually located in the same row as the center sub-pixel of the group of three sub-pixels RPij, GPij, BPij, which together can provide the same color as the fourth sub-pixel WPij. . The first component RIl1, the second component GIl1, and the third component BIl1 of the first sample S11 are the first component RD11, the second component GD11, and the third of the sample D11, respectively. The first sub-pixel RP11, the second sub-pixel GP11, and the third sub-pixel BP11 of the first set P11 of four sub-pixels are mapped to the component BD11, respectively. Mapped onto the phase. The fourth component WI12 of the sample S12 is mapped to the fourth component WD11 of the sample DI1 and thus to the fourth sub-pixel WP11 of the first set P11. The fourth component WI21 of the sample S21 is mapped to the fourth component WD21 of the sample D21 and thus to the fourth sub-pixel WP21 of the second set of adjacent sub-pixels P21. Mapped. The first component RI22, the second component GI22, and the third component BI22 of the sample S22 are the first component RD21, the second component GD21, and the third component D21 of the sample D21, respectively. Mapped to component BD21 and thus to first sub-pixel RP21, second sub-pixel GP21, and third sub-pixel BP21 of second set P21.

FIG. 5 shows a broadcast system providing information including signals for driving four primary color sub-pixels RPij, GPij, BPij, WPij. The broadcast system includes a distribution station BR which provides information INF to the displays of users U1, U2, U3. The information INF may be the same for the users, or may be tailored according to the personal wishes of the users. Information INF is for each set Pij of the four sub-pixels RPij, GPij, BPij, WPij of the user's display DD, the first, second, And a fourth input signal WI12 of the third (RI1, GI1, BI1) input signal and the adjacent input sample S12.

FIG. 6 schematically shows a block diagram of a display device including a system for converting a three-primary input color signal into an N-primary driving signal. The system for converting the 3-primary input color signal IS into the N-primary drive signal DS includes a multi-primary conversion unit 10, a constraint unit 20, and a parameter unit 30. These units may be hardware or software modules. The constraint unit 20 provides the constraint CON to the transformation unit 10. The parameter unit 30 provides the primary color parameters PCP to the conversion unit 10.

The conversion unit 10 receives the three primary color input signal IS and provides an N-primary color driving signal DS. The three primary input signal IS comprises a sequence of input samples each comprising three input components R, G and B. The input components (R, G, B) of a particular input sample define the color and intensity of the input sample. The input samples may be samples of an image, eg, samples of an image generated by a camera or a computer. The N-primary drive signal DS comprises a set of drive samples each comprising N drive components D1 -DN. The drive components D1-DN of a particular output sample define the color and intensity of the drive sample. Normally drive samples are displayed on the pixels of the display device 3 via a drive circuit 2 which processes the drive samples, so that output samples are obtained suitable for driving the display 3. The driving components D1 to DN define driving values O1 to ON for the sub-pixels SP1 to SPN of the pixels. In FIG. 1 only one set of sub-pixels SP1 to SPN is shown. For example, in an RGBW display device, the pixels have four sub-pixels SP1-SP4 that provide red (R), green (G), blue (B), and white (W) light. The particular drive sample has four drive components D1-D4 that generate four drive values O1-O4 for the four sub-pixels SP1-SP4 of the particular pixel.

The display device comprises a signal processor 4 which receives an input signal IV which reproduces the image to be displayed in order to provide a three primary color input signal IS. The signal processor 4 may be a camera, with no input signal IV present. The display device may be part of a portable device such as, for example, a mobile phone or a personal digital assistant (PDA).

7 shows a graph for explaining an embodiment of a further equation. 7 shows an example in which N = 4. The graph shows three drive components D1-D3 as a function of the fourth drive component D4. The fourth drive component D4 is shown along the horizontal axis, and the three drive components D1-D3 are shown along the vertical axis along with the fourth drive component D4. In general, the drive components D1-D3 are used to drive sets of sub-pixels of the display 3, also referred to as drive signals hereinafter. The drive components D1-D4 of the same drive sample can drive sub-pixels of the same pixel. Alternatively, the driving components D1-D4 of adjacent samples may be sub-sampled into sub-pixels of the same pixel. Now, not all driving components D1-D4 are actually assigned to sub-pixels.

Three drive signals D1 to D3 are defined as a function of the fourth drive signal D4: F1 = D1 (D4), F2 = D2 (D4), F3 = D3 (D4). The fourth driving signal D4 is a straight line passing through the origin, and the first derivative is one. The valid ranges of the four drive signals D1-D4 have been normalized to the 0-1 range. The common range VR of the fourth drive signal D4 in which all four drive signals D1 to D4 have values within their valid ranges is D4min to D4max, and includes these boundary values.

In this example, a linear light region is selected in which the functions defining the three drive signals D1-D3 as a function of the fourth drive signal D4 are defined as linear functions:

Here, D1 to D3 are three driving signals, (P1 ', P2', P3 ') are defined by an input signal which is generally an RGB signal, and coefficients ki are three driving values D1 to D3. Define the dependence between the color points of the three primary colors associated with D3) and the primary colors associated with the fourth driving signal D4. In general, these coefficients are fixed and can be stored in memory.

To further illustrate the relationship between the elements of these functions, it is now disclosed how the functions relate to the standard three to four primary color transform. In the standard 3-4 primary color conversion, the drive signal DS including the drive signals D1 to D4 is converted into the linear color space XYZ by the next matrix operation.

Equation 1

The matrix of coefficients tij defines the color coordinates of the four primary colors of the four sub-pixels. The drive signals D1-D4 are unknown, which must be determined by multi-primary conversion. This equation (1) cannot be solved immediately because there are a plurality of possible solutions as a result of introducing the fourth primary color. A specific selection from these possibilities for the drive values of the drive signals D1-D4 is obtained by applying a constraint, which is a fourth linear equation added to the three equations defined by equation (1). Lose.

This fourth equation values the linear combination of the first subset of N drive components (D1, ..., DN) and the second subset of N drive components (D1, ..., DN). Obtained by definition. The first subset includes a first linear combination LC1 of 1≤M1 <N of N driving components D1, ..., DN, and the second subset includes N driving components D1, Second linear combination LC2 of 1 < = M2 &lt; The first and second linear combinations are different. Both the first and second linear combinations can include only one drive component or several drive components. The solution for the N driving components D1, ..., DN is found by solving the extended set of equations. Preferably, the driving components in the first set are not in the second set and are in another way such that the linear combinations LC1, LC2 point to different sub-groups of sub-pixels belonging to the same pixel.

In this example, the linear combination LC1 is associated with the weighted luminance of the first sub-group of the sub-pixels of the pixel, and the linear combination LC2 is the weighting of the second sub-group of other sub-pixels of the same pixel. Associated luminance. The other equation thus defines a linear combination of weighted luminance equal to the value. The first sub-group of sub-pixels and the second sub-group of sub-pixels may comprise only one sub-pixel, and do not need to contain all the sub-pixels of the pixel together.

Preferably, the first linear combination LC1 defines the brightness of the drive components of the first subset and the second linear combination LC defines the brightness of the drive components of the second subset. Thus, the linear combination LC1 directly represents the luminance produced by the sub-pixels associated with the drive components that are members of the first subset. And the linear combination LC2 directly represents the luminance produced by the sub-pixels associated with the drive components that are members of the second subset. The value defines a constraint on the linear combination of these luminances. For example, this constraint may indicate that the luminance of the first linear combination is second linear in order to obtain the minimum amount of artifacts caused by overly different luminance of adjacent sub-pixels SP1-SPN of the same pixel. It must be equal to the brightness of the combination. For this same luminance constraint, the linear combination of the first and second subsets is subtraction and the value is almost zero. This same brightness constraint will be described with respect to other embodiments with reference to FIGS. 7 and 8.

First, however, in the following, a method is described in which functions for defining three drive signals D1 to D3 as a function of the fourth drive signal D4 are determined.

Equation (1) can be rewritten as:

Equation 2

Here, matrix [A] is defined as a transformation matrix in the standard three primary color system. Multiply the terms of equation (2) by the inverse [A ^-1 ] to obtain equation (3):

Equation 3

The vector [P1 'P2' P3 '] represents the primary color values obtained when the display system contains only three primary colors and is defined as the vector [Cx Cy Cz] multiplied by the inverse matrix [A- ¹ ]. Finally, equation (3) can be rewritten as equation (4).

Equation 4

Thus, the drive signal of any of the three primary colors D1-D3 is represented as a function of the fourth primary color D4 by equation (4). These linear functions F1 to F3 define three lines in the two-dimensional space defined by the values of the fourth primary color D4 and the fourth primary color D4, as illustrated in FIG. All values in FIG. 7 have been normalized, which means that the values of the three driving values D1 to D4 should be in the range of 0 ≦ Di ≦ 1. From Fig. 7, it is directly and visually clear what is the common range VR of D4, in which all the functions F1 to F3 and the fourth drive signal D4 have values within the valid range. It should be noted that the coefficients k1-k3 are predefined by the color coordinates of the sub-pixels associated with the drive values D1-D4.

In the example shown in Fig. 7, the boundary D4min of the valid range VR is determined by a function F2 having a value greater than 1 for values of D4 smaller than D4min. The boundary D4max of the valid range VS is determined by a function F3 having a value greater than 1 for values of D4 that are greater than D4max. Basically, if no such common range VR exists, the input color is outside the four primary color gamut, and thus cannot be reproduced correctly. A clipping algorithm that fixes these colors to the color range should be applied for these colors. A method for calculating common ranges (D4min-D4max) is described in the unpublished European patent application 05102641.7, which is incorporated herein by reference. The presence of the common range VR indicates that there are many possible solutions for converting certain values of the three input components R, G, B into four drive components D1-D4. The effective range VR is any possible value of the driving component D4 that provides a transformation such that the intensity and color of the four sub-pixels correspond to that represented by exactly three input components R, G and B. Include them. The values of the other three drive components D1-D3 are obtained by substituting the selected value of the drive component D4 into equation (4).

7 also shows lines LC1 and LC2. Line LC1 represents the luminance of the driving components D4, and line LC2 represents the luminance of the driving components D1 to D3. Thus, only the first subset of N drive components includes a weighted drive component D4 to represent the luminance of the associated sub-pixel. The second subset of N drive components includes a weighted linear combination of three drive components D1-D3, wherein the linear combination is of the sub-pixels associated with these three drive components D1-D3. Indicate the luminance of the combination. At the intersection of these lines LC1 and LC2 with respect to the drive value D4opt, the brightness of the drive component D4 is equal to the brightness of the combination of the drive components D1 to D3.

This same luminance constraint is of particular interest to a spectral sequential display 3 which drives one set of primary colors during even frames and drives the remaining sets of primary colors during odd frames. The algorithm uses the input components (under the same luminance constraint) such that the luminance produced by the first subset of sub-frames during even frames is the same as the luminance produced by the second subset of sub-pixels during odd frames. The given input color defined by R, G, B is treated as output components D1-DN. Thus, the first subset of N driving components drives the first subset of sub-pixels during even frames, and the second subset of N driving components is the second subset of sub-pixels during odd frames. To drive. If it is impossible to represent the same brightness for both frames for a given input color, then the input color is adjusted to a value that allows the same brightness, or the output components are adjusted to obtain the same brightness as possible.

For example, in an RGBY (R = red, G = green, B = blue, Y = yellow) display, only blue and green sub-pixels are driven in even frames, while only red and yellow sub-pixels are odd. Driven in frames. Of course any other combination of colors is also possible. In this example, in Fig. 2, two lines LC1 and LC2 represent the luminance of blue plus green driving components and the luminance of yellow and red driving components, respectively. The value D4opt of the driving component D4 at which these two lines LC1 and LC2 intersect is an optimal value in which the luminance of the blue and green sub-pixels is the same as the luminance of the red and yellow sub-pixels. This method minimizes temporary flicker.

In fact, equation (1) was extended by adding a fourth row to matrix T. The fourth line defines additional equations:

t21 * D1 + t22 * D2-t23 * D3-t24 * D4 = 0

Since Cy defines luminance, the coefficients are t21 to t24. The first subset includes a linear combination of drive values D1 and D2, and the second subset includes a linear combination of drive values D3 and D4, with a value of zero. This additional equation adds the same brightness constraint to equation (1). Thus, the solution of the extended equation is on the one hand with respect to the sub-pixels SP1, SP2 driven by the driving components D1, D2 and on the other hand with the sub- driven by the driving components D3, D4. The same luminance is provided for the pixels SP3 and SP4. Extended equations are defined by:

[Equation 5]

Equation (5) can be easily solved by calculating:

Here, [TC ^-1 ] is the inverse of [TC].

When all drive components D1 to D4 have valid values that are true when 0 ≦ Di ≦ 1 (i = 1 to 4) if normalized, the answer to drive components D1 to D4 is meaningful. . For some input colors defined by the input components R, G, B, this may not be achieved. The optimal drive value D4opt of the drive component D4 corresponds to a drive value that allows flicker-free operation and is defined by the following equation:

[Equation 6]

The coefficients TC41, TC42, TC43 do not depend on the input colors. The values of the other drive components D1-D4 are calculated using equation (4). If the optimal drive value D4opt occurs in the effective range VR, the solution provides the same brightness in both even and odd sub-frames.

If the optimum drive value D4opt does not occur in the effective range VR, this value is adjusted to the nearest boundary value D4min or D4max, and this adjusted value is equal to the other drive components in equation (4). It is used to determine the values of (D1 ~ D3). Now, the luminance is not the same in even and odd sub-frames. However, the error is minimized by adjusting to the nearest boundary value. The luminance is defined by the error:

Here, the substitution of equation (4) yields the following:

This is zero if D4opt is not adjusted. However, clipping adds the error for D4 to the optimal value D4opt. The resulting luminance error is as follows:

It should be noted that the k1 * t21 + k2 * t22-k3 * t23-t24 terms are constant, so that the luminance error DELTA L is determined only by the error value DELTA D4. As a result, the minimum error of the driving component D4 causes the error of the luminance of the sub-pixel groups during the different sub-frames to be minimal.

By adding a fourth equal luminance equation to the three equations defining the relationship between the three input components R, G, B and the four drive components D1-D4, the three input components R The method of converting G, B to four driving components D1 to D4 may include any spectral sequential display having four primary colors provided by four sub-pixels SP1 to SP2. Very efficient for). There are no restrictions on the color points of the primary colors. This algorithm can also be used directly for six primary colors systems as part of the transformation. This algorithm can also be used for any number of primary colors (sub-pixels per pixel) greater than four. In general, however, this will give a range of possible solutions if none of the above constraints are met. One advantage of this approach is that large and expensive lookup tables are avoided. Only 17 multiplications, 14 additions, and 2 min / max operations per sample need to be performed, so the conversion is cheap.

8 shows a graph for explaining another embodiment of a further equation. 8 shows an example where N = 4, the display is an RGBW display, and the fourth equation is the same luminance constraint. In this example, in an RGBW display, drive component D1 drives a red sub-pixel, drive component D2 drives a green sub-pixel, drive component D3 drives a blue sub-pixel, And drive component D4 drives the white sub-pixel. Now, if possible at certain values of the three input components R, G, B, the luminance of the RGB sub-pixels remains the same as the luminance of the white pixel to minimize spatial non-uniformity. If the color of a single sub-pixel can be generated by a combination of three different sub-pixels, other colors can be used instead of RGBW.

8 shows three drive components D1-D3 as a function of the fourth drive component D4. The fourth drive component D4 is shown along the horizontal axis, and three drive components D1 to D3 along with the fourth drive component D4 are shown along the vertical axis. In general, the drive components D1-D3 are used to drive the sub-pixels of the display 3, also referred to as drive signals hereinafter. Driving signals D1 to D4 of the same driving sample may drive sub-pixels of the same pixel. Alternatively, the driving components D1-D4 of adjacent samples may be sub-sampled into sub-pixels of the same pixel. Now, not all driving components D1-D4 are actually assigned to sub-pixels.

Three drive signals D1 to D3 are defined as a function of the fourth drive signal D4: F1 = D1 (D4), F2 = D2 (D4), F3 = D3 (D4). The fourth driving signal D4 is a straight line passing through the origin, and the first derivative is one. In this example, a linear light region in which the functions F1 to F3 are straight lines is selected. The effective range of the four drive signals D1 to D4 is normalized to the 0 to 1 range. The common range VR of the fourth drive signal D4 in which all three drive signals D1 to D3 have values within their effective ranges is D4min to D4max and includes these boundary values.

In this embodiment, the line F4 represents the luminance of the white sub-pixel SP4. Line Y (D4) represents the combined luminance of the RGB sub-pixels SP1-SP3 for the particular three input components R, G, B. The luminance represented by the line Y (D4) is the luminance of the white (W) sub-pixel such that the combined luminance of the RGB sub-pixels SP1 to SP3 is equal to the luminance of the W sub-pixel SP4. Normalized forward. This intersection occurs at the value D4opt of the drive component D4. Again, the values of the other drive components D1-D3 are obtained by substituting D4opt into equation (4).

In the special case where the chromaticity diagram of the W sub-pixel SP4 is produced by the RGB sub-pixels SP1 to SP3 coincides with the white point, the functions F1 to F3 become simpler: All coefficients k1 to k3 in (4) have the same negative value. Thus, the lines representing the functions F1-F3 intersect the line P4 = P4 under the same angle. If the maximum possible luminance of the W sub-pixel SP4 is equal to the maximum possible luminance of the RGB sub-pixels SP1 to SP3, then all the coefficients k1 to k3 of equation (4) have a value of -1. The lines representing the functions F1 to F3 intersect the line P4 = P4 at 90 degrees.

This scheme adds a fourth linear equation that defines the same luminance constraint to three equations that define the relationship between the four drive components D1-D4 and the three input components R, G, B. Improves the spatial homogeneity between the RGB and W sub-pixels. In fact, equation (1) was extended by adding a fourth row to the matrix T. The fourth line defines additional equations:

t21 * D1 + t22 * D2 + t23 * D3-t24 * D4 = 0

Since Cy defines luminance in the linear XYZ color space, the coefficients are t21 to t24. The first subset includes a linear combination of drive values D1, D2, D3 for driving RGB sub-pixels SP1, SP2, SP3. The second subset includes a linear combination that includes only the drive value D4. This additional equation adds the same brightness constraint to equation (1). Thus, the solution of the extended equation is on the one hand for the combined luminance of the sub-pixels SP1, SP2, SP3 driven by the driving components D1, D2, D3 and on the other hand the driving component D4. Provide the same luminance for the sub-pixel SP4 driven by &lt; RTI ID = 0.0 &gt;

The extended equation is defined as follows:

[Equation 7]

Equation (6) can be easily solved by calculating:

Here, [TC'- ¹ ] is the inverse of [TC '].

The optimal drive value D4opt of the drive component D4 corresponds to the drive value that allows the lowest spatial homogeneity and is therefore defined by the following equation:

Equation 8

It should be noted that equation (8) has the same structure as equation (6), only the matrix coefficients are different.

As discussed in the example of FIG. 2, when the determined optimal drive value is outside the effective range VR, this optimal drive value is clipped to the nearest boundary value D4min or D4max.

9 shows a block diagram of an embodiment according to the present invention. The dashed block 5 is identical to the system 1 for converting a three-primary input color signal IS into an N-primary drive signal DS. However, in Fig. 6, the three-primary input color signal IS is an RGB signal that does not need to be defined in the linear light region. In FIG. 9, it is assumed that the three-primary input color signal IS is defined in the linear light region by the input components Cx, Cy, Cz of the linear XYZ color space. The three-primary input color signal IS can be defined directly in the linear XYZ color space, or first converted from a non-linear color space, such as the RGB color space, to a linear XYZ color space. The conversion system 5 includes a calculation unit 51, a clipping unit 52, a calculation unit 53, an interval unit 50, and a storage unit 54. These units may be implemented in hardware or software modules.

The interval unit 50 receives the input components Cx, Cy, and Cz and determines the boundary values D4min and D4max of the fourth driving component D4. In addition, the interval unit 50 calculates values for a vector P1 'P2' P3 'representing primary color values obtained when the display system includes only three primary colors. This vector is defined by the following equation, as described with respect to equations (2) and (3):

Here, [A ^-1 ] is the inverse of the matrix [A] defined in equation (2). Thus, the values of the components P1 ', P2', P3 'of this vector depend on the values of the input components Cx, Cy, Cz.

The storage unit 54 stores both the values of the coefficients k1, k2, k3 and the values B1, B2, B3 of the equation (4). The values B1, B2, B3 depend on the application. In the embodiment discussed with respect to Figure 2, the optimal drive value D4opt of the drive component D4 is defined by equation (6). The coefficients TC41, TC42, TC43 may be stored in advance without being dependent on the input color. Thus, for this embodiment, the values B1, B2, B3 are equal to the coefficients TC41, TC42, TC43, respectively. In the embodiment discussed with reference to FIG. 3 for an RGBW display 3, in which spatial homogeneity is optimized, the optimum drive value D4opt of the drive component D4 is defined by equation (8). Further, the coefficients TC41 ', TC42', TC43 'can now be stored in advance without being dependent on the input color. Thus, for this embodiment, the values B1, B2, B3 are equal to the coefficients TC41 ', TC42', TC43 ', respectively.

The calculating unit 51 receives the input components Cx, Cy, Cz and the values B1, B2, B3 and, according to equation (6) or (8), the optimum drive value D4opt of the drive component D4. Is determined. The clipping unit 52 receives the optimal driving value D4opt and the boundary values D4min and D4max and provides an optimal driving value D4opt '. The clipping unit 52 determines whether the optimum driving value D4opt calculated by the calculating unit 51 is within the effective range VR having the boundary values D4min and D4max as determined by the interval unit 50. Check it. If the optimum drive value D4opt is in the effective range VR, the optimum drive value D4opt 'is equal to the optimum drive value D4opt. If the lowest drive value D4opt is outside the effective range VR, the optimum drive value D4opt 'becomes equal to the boundary value D4min or D4max closest to the optimum drive value D4opt.

The optimum drive value D4opt 'is the output component D4 of the output signal DS of the conversion system 5. The calculating unit 53 substitutes the output component D4 into the equation (4) to calculate other output components D1 to D3.

Note that, for the same luminance constraints for the spectral order display 3 and the RGBW display, the embodiments have been described in the case of N = 4. However, the scope of the present invention is broader as defined by the claims. The same method is possible for N> 4. Linear of the first subset of N driving components D1, ..., DN and the second subset of N driving components D1, ..., DN to obtain an extended set of equations The addition of at least a linear equation defining the value for the combination will narrow the possible solutions to those defined by the constraints imposed by the linear equation. This linear equation imposes a weighted luminance constraint on the different sub-sets of driving components D1,..., DN. For example, it is possible for N> 4 to combine this luminance constraint with another constraint such as the minimum of the maximum value of the driving components D1-DN.

The algorithm is very attractive for portable or mobile applications using a spectrum sequential multicolor display. However, the algorithm can be used for other spectral-sequential applications, such as TV, computer, medical displays, where the main disadvantages of the spectral-sequential approach and flicker are required to be avoided. The algorithm can be used only for specific color components or only for specific ranges of the input signal. For example, the algorithm may not include driving components for sub-pixels that do not contribute or only minimally contribute to flicker. Or, the algorithm is not used for saturated or bright colors.

It should be noted that in typical user systems, including cameras, printers, and displays, it is important that the correct colors are printed and displayed. Thus, the image information exchanged between the camera and the printer or display device must be in a universal format. This general purpose format is preferably the XYZ color space. The device receiving the image from the camera has a color management module that converts an image of the XYZ color space into the color space required by the device. In the printer, this color management module converts an image in XYZ space into a CMY color space. In the display, the color management module converts the XYZ spatial image into an RGB color space. However, in the display according to the invention, the color management module in the display converts an image of the XYZ space into a color space defined by the four primary colors of the four sub-pixels. This conversion can be performed directly or through the RGB color space.

It should also be noted that the foregoing embodiments do not limit the invention, and that those skilled in the art may design various alternative embodiments without departing from the scope of the appended claims.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The verb “comprises” and derivatives thereof does not exclude the presence of elements or steps other than those stated in a claim. The singular expression of the component does not exclude that the component may exist in plural. The invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means can be embodied as one and the same item of hardware. The fact that certain means are cited in different dependent claims does not indicate that a combination of these means cannot be used to advantage.

Indeed, the components of the algorithms disclosed herein may be implemented in whole or in part as hardware, or as software operating in a special digital signal processor or general purpose processor or the like. The hardware may be part of an application specific IC.

It is to be understood that a computer program product is a set of instructions that enable a general purpose or special purpose processor to perform some of the characteristic functions of the present invention. The instructions may be loaded into the processor in one step or in a series of loading steps. The series of loading steps may include intermediate conversion steps such as, for example, translation into an intermediate language, and / or a final processor language. In particular, the computer program product may be embodied as disk or tape, data on a carrier such as a memory, data transmitted over a wired or wireless network connection, or program code on another medium such as paper. Except for the program code, the characteristic data required for the program can be implemented as a computer program product. For example, some of the steps required for the performance of the method, such as data input and output steps, may already be present in the function of the processor instead of being defined in a computer program product.

Claims (15)

A method of mapping a 4-primary input signal IS to sets Pij of four sub-pixels RPij, GPij, BPij, WPij of the display device DD, The four-primary input signal IS may have a value for the first component RIij, a value for the second component GIij, a value for the third component BIij, and a fourth component WIij, respectively. A sequence of input samples (Sij) containing a value for The sets of four sub-pixels Pij are a first sub-pixel RPij for providing light with a first primary color R, a second for providing light with a second primary color G. A sub-pixel GPij, a third sub-pixel BPij for providing light having a third primary color B, and a fourth sub-pixel WPij for providing light having a fourth primary color W; ), Wherein the first, second, third, and fourth colors are all different, the fourth color is within the color range of the first, second, and third colors, The method comprises a first component RP11 of a specific input sample S11, a second component GI11, and a third component BI11 of a first set RP11 of a particular set of four adjacent sub-pixels P11. The second component GP11 and the third sub-pixel BP11, respectively, and assign the fourth component WI12 of another input sample S12 to the specific set of four adjacent sub-pixels S11. Sub-sampling (MAP) the input samples (Sij) of the four primary color input signals (IS) by assigning them to a fourth sub-pixel (WP11). Another input sample (S12) is associated with adjacent positions on the display device (DD). The method of claim 1, And wherein the first primary color (R) is red, the second primary color (G) is green, and the third primary color (B) is blue. The method of claim 2, The display device DD is illuminated by a backlight unit BL, a red filter RF is associated with the first sub-pixel RPij, and a green filter GF is the second sub-pixel GPij. ), And a blue filter (BF) is associated with the third sub-pixel (BPij), and the light (BLL) generated by the backlight unit (BL) is not filtered, the fourth sub- A sub-pixel mapping method that passes through a pixel WPij. The method according to any one of claims 1 to 3, And said fourth color (W) is white. The method of claim 1, In the 4-primary input signal IS, the other input sample S12 is the sub- of the first, second, and third sub-pixels RPij, GPij, BPj in the set Pij. Located in relation to the particular input sample (S11) so as to correspond to the position of the fourth sub-pixel (WPij) in relation to a group. The method of claim 5, The other input sample S12 immediately preceding or following the specific input sample S11 in a specific line of the video input image, The method further comprises sub-sampling the third input sample S21 and the fourth input sample S22 into another set of sub-pixels, The other set of sub-pixels is a fifth sub-pixel RP21 for providing light with the first color R, a sixth sub-pixel for providing light with the second color G. GP21, a seventh sub-pixel BP21 for providing light having the third color B, and an eighth sub-pixel WP21 for providing light having the fourth color W Including, The sub-sampling is performed by the first component RI22, the second component GI22, and the third component BI22 of the fourth input sample WI22 by the fifth (RP21), the sixth (GP21), and the seventh. (BP21) assigning each to a sub-pixel, and assigning a fourth component WI21 of the third input sample S21 to the eighth sub-pixel WP21, In the 4-primary input signal IS, the fourth input sample S22 is the sub- of the fourth, fifth and sixth sub-pixels RP21, GP21, BP21 in the set P21. Positioned relative to the third input sample S21, corresponding to the position of the eighth sub-pixel WP21 relative to the group, the fourth input sample S22 being located at another specific line of the video input image. Directly preceding or following the third input sample S21, and the other specific line immediately preceding or following the specific line, and the specific line and the other specific line may extend vertically or horizontally, Sub-pixel mapping method. A method of driving a display device DD having sets Pij of four sub-pixels RPij, GPij, BPij, WPij, On the one hand, three primary colors are input under the same brightness constraints on the luminance of the combination of the first component RIij, the second component GIij, and the third component BIij, and on the other hand the luminance of the fourth component WIij. Converting the signal TIS into a four primary color input signal IS MPC; And And mapping (MAP) as claimed in claim 1. A computer program product comprising processor readable code for enabling a processor to execute the method of claim 1, comprising: The processor readable code may include a first component RI11, a second component GI11, and a third component BI11 of a particular input sample S11 of a particular set of four adjacent sub-pixels P11. Assigning the first component RP11, the second GP11 and the third sub-pixel BP11, respectively, and assigning the fourth component WI12 of another input sample S12 to the four adjacent sub-pixels. Code for assigning to the fourth sub-pixel WP11 of the set S11 to sub-sample input samples Sij of a four primary color input signal IS, The particular input sample (S11) and the other input sample (S12) are associated with adjacent positions on the display device (DD). The method of claim 8, The computer program product is a software plug-in within an image processing application. A system for mapping a 4-primary input signal IS to sets Pij of four sub-pixels RPij, GPij, BPij, WPij of a display device DD, The four-primary input signal IS may have a value for the first component RIij, a value for the second component GIij, a value for the third component BIij, and a fourth component WIij, respectively. A sequence of input samples (Sij) containing a value for The sets of four sub-pixels Pij are a first sub-pixel RPij for providing light with a first primary color R, a second for providing light with a second primary color G. A sub-pixel GPij, a third sub-pixel BPij for providing light having a third primary color B, and a fourth sub-pixel WPij for providing light having a fourth primary color W; ), Wherein the first, second, third, and fourth colors are all different, the fourth color is within the color range of the first, second, and third colors, The system comprises a first component (RI11), a second component (GI11), and a third component (BI11) of a particular input sample (S11) of the first (RP11) of a particular set (P11) of four adjacent sub-pixels. ), The second set GP11, and the third sub-pixel BP11, respectively, and assign the fourth component WI12 of another input sample S12 to the specific set of four adjacent sub-pixels ( And a mapper (MAP) for sub-sampling the input samples Sij of the four primary color input signals IS by allocating to a fourth sub-pixel WP11 of S11, wherein the specific input sample S11 is included. And the other input sample (S12) is associated with adjacent positions on the display device (DD). In a circuit for driving a display device DD having sets Pij of four sub-pixels RPij, GPij, BPij, WPij, On the one hand, three primary colors are input under the same brightness constraints on the luminance of the combination of the first component RIij, the second component GIij, and the third component BIij, and on the other hand the luminance of the fourth component WIij. A converter MPC for converting the signal TIS into a four primary color input signal IS; And A display device drive circuit comprising the system as claimed in claim 10. A display device comprising the display device having the circuit of claim 11 and the sets Pij of four sub-pixels (RPij, GPij, BPij, WPij). A portable device comprising a display device having the circuit of claim 11 and sets of four sub-pixels (RPij, GPij, BPij, WPij). In a broadcast system, A distribution station BR for providing information INF to the displays of users Ui, The distribution station BR comprises the system of claim 10, The information INF is the first, first of a particular input sample S11 for a particular set Pij of four sub-pixels RPij, GPij, BPij, WPij of the displays of the users U1. 2, a third component (RI11, GI11, BI11) and a fourth component (WI12) of the other input sample (S12). In the broadcasting method, Providing (BR) the information INF to the displays of the users Ui, Providing (BR) comprises performing the method of claim 1, The information INF is the first, first of a specific input sample S11 for a particular set Pij of four sub-pixels RPij, GPij, BPij, WPij of the displays of the users Ui. 2, the third component (RI11, GI11, BI11) and the fourth component (WI12) of the other input sample (S12).

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